Wits, that is what I think Kjs needs.
Kjs - take control. Just because "difficult child forbids it", doesn't mean you have to take a back seat and let him drive.
There are different ways to handle this situation. difficult child 2's best friend (also autistic) - his father is built like Arnie, his mother is fearless. She drove up to a group of kids she knew were bullying her son and told them that if she ever heard that they were hassling her son again, she would be back. I can sympathise with that approach although I think it is too risky - you become a bully unnecessarily, I think. Mind you, I would do that if I ran out of all other, more legal, options.
The legal options - find out what the law is in your area. Talk to the police. Talk to the school. Find out if there is an advocacy service in your area.
You are worried about repercussions against difficult child if you take any action? Well, what about what he's copping now? Surely that can't be tolerated? A lot of regulations, where regulations exist, make specific mention of strong action which can be legally taken against anyone who seeks retribution purely for complaints made. It ups the ante of the original offence, if the culprit then takes further action. It doesn't matter who the culprit attacks or who made the complaint, ANY further action against anyone which has resulted from a complaint being made, the authorities will come down even harder on.
First step - the ISP. Contact the sites where this is going on. You can generally find them on a "contact us" button, there can be a specific button for dealing with abuse of site rules. Look for it and use it. Anyone can complain - some totally anonymous person who doesn't know difficult child at all, could see the abuse and report it. Or a moderator on the site could deal with it. Any repercussions - difficult child can claim to not have made any complaints, but if there ARE repercussions the authorities need to be notified. Again.
Keep detailed notes. The screen shots are a very good idea. When we went through this (first with me and my online stalkers, then with easy child 2/difficult child 2 and ex-boyfriend's nasty blogging) we copied it all to a text file with dates and any other notes, and refrained from responding. That is important. difficult child is too young/immature to know this, but failure to respond is ALWAYS a good tactic. And especially so with the Internet, where failure to respond indicates a 'dead' link - the person has moved on to greener pastures. (example - never respond to spam, even if it's clicking 'unsubscribe'. A lot of spammers are unscrupulous, and trying to unsubscribe can get you an avalanche of spam from many more sources.)
Next step - report this as serious abuse, bullying and antisocial behaviour. This is known to cause harm. The laws are there, often it's a matter of finding out which law can be interpreted to provide protection. Sometimes you need to go through certain steps first - with my first stalker, I knew who he was. I made enquiries with local authorities on what I could do, which led to how I had to go about it. In my case, I needed to demonstrate with a paper trail that this contact was continuing after I had formally requested it to cease and desist. I sent a carefully worded letter to him (I got the wording from the local authorities) saying that while I was prepared to exchange polite greetings in public when witnesses were present, all other contact from him in writing (of any form, electronic or otherwise) to me or any member of my family was to immediately cease permanently, as it was causing considerable inconvenience and needless distress (in his case, he was not intending to cause distress to me or my children, he was only trying to vent his anger). My letter went on to say that failure to observe this restriction would result in immediate legal action being taken to set up and enforce a protection order. I was also advised that trying to organise mediation with him, and failing due to his refusal, would almost guarantee my success in getting a protection order.
In my case, that was enough - all contact in writing ceased. He did try it on briefly, we dealt with that smartly and have had no more trouble with him in that way. I think he's now lost interest in annoying me and my family.
Sometimes all it takes is your clear, considered and legal response to totally terrify a bully into leaving you alone. As long as you put up with it (on the basis that it will only get worse if you complain) then you are giving the bullies permission to continue. You are also sending a message that you are afraid - to the bully, and to your child. You use the whole process as a learning experience for the bully, and for your child, on the appropriate ways to deal with this sort of thing. You respond - appropriately - and if the problem continues, your paper trail helps you respond even more effectively next time.
Your difficult child has been copping heaps from his bullies for some time. He is getting the message that it is his lot in life to be bullied. No kid deserves that.
There were times when my children had a problem with a teacher at school, or a bully, told me about it but begged me to not get involved. However, where I felt it was necessary I DID get involved. They now thank me for it. By getting involved I confronted their fear for them. I also made it clear to the bully that any attempt to take reprisals BY ANYONE against my child(ren) following from my visit would result in another, louder, visit from me, with any legal authority I could bring to bear. Generally this was enough to make them leave my child alone. And by stressing BY ANYONE I made it clear that I would take it as a personal attack, if it was even a DIFFERENT bully who had a go at my child. This meant that the bully now had a vested interest to not only leave my child alone, but to make sure others did as well.
I made sure I did this entirely within our rights by law. I have been told by some (including here) that this tactic of mine could also be considered bullying. However, when given as a response to bullying, when all other options have been tried or are not available, I consider this valid as "defence" response.
Your difficult child needs to learn that dishing out negativity will bring it back home to him. He can't insist on being treated kindly, if he does this himself to others. Whatever standards you require of others, you must ensure you comply with as well (here, 'you' also means difficult child). This can be an important, positive, lesson for him to learn.
As for "being friends" one day, and being nasty the next - I suspect the bully was only pretending to be a friend to 'fatten him up'. Or it could be similar to an experience difficult child 1 had at about this age - his best friend at the time, who he would visit to play computer games with, was presented with a choice: join the gang and be considered 'cool', or continue to be friends with difficult child 1 but be out in the cold. The friend chose to join the gang, but to prove himself he had to set up difficult child 1 for an attack (which would also permanently sever ties with difficult child 1, the 'good but not cool' kid).
This friend now has a criminal record, has been using and dealing in drugs for some years and is STILL being led by the nose by his nasty gangster 'friends'. The only reason he has a criminal record is because he was trying to protect his friends (who happily let him take the punishment and the record). Some friends.
Standing your ground now will lose difficult child some friends. But they are friends he can well do without and who clearly are not REAL friends. It draws the line in the sand which says, "you can go here, but no further."
And I would never, ever, let difficult child have a personal web page ever again, that reveals anything about his true identity or location. Maybe "secret identity" might appeal to difficult child. Chuck the other pages - check out Gaia instead. Only let him use a disposable email address from yahoo or similar.
And if all else fails - find out this other person's email address and send it to every Nigerian scammer, seller of online pharmaceuticals, sender of glurge etc that you can find. Cram their in box with rubbish so it's so full they have to shut down operations and clan it all up.
A bad idea really, but it's nice to dream...
Marg